Episode: 4330
Title: HPR4330: GIMP: Fixing Photos
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr4330/hpr4330.mp3
Transcribed: 2025-10-25 23:10:22

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This is Hacker Public Radio episode 4,330 for Friday the 7th of March 2025.
Today's show is entitled Gimp Fixing Photos.
It is part of the series Gimp.
It is hosted by Ahukah and is about 16 minutes long.
It carries a clean flag.
The summary is how to fix some of the common problems in photos.
Hello, this is Ahukah, welcoming you to Hacker Public Radio in another exciting episode
in our Gimp series.
It's been a while since we did this, but I always said that what I wanted to do was not
just talk about Gimp in general terms, but to focus on fixing up some photos.
And I've got some free time, so I thought this is a good time to dig into this.
So this is going to be the first of what might be two, I don't know, episodes on fixing
common problems with photos.
Now I can only deal with the things that I have dealt with, so there may be other photo
issues that I don't cover, because it just hasn't really happened to me.
But what I want to do here is take a look at a few common issues that, you know, sometimes
you just need to fix problems with a photo, or even a number of photos.
Now in my case, I have a lot of photos from our various trips.
Now according to Flickr, where I have a pro account, I have at the time of writing 13,000
photos, and I don't plan to stop.
Now managing all of this can get tricky.
I generally start with DigiCam, which is my photo manager of choice.
I tend to store my photos by date with each day being its own directory.
So it's easy to load all of the photos from a given day in DigiCam, and from there I
can click the preview button to see the photo in a larger size than the thumbnail.
You can navigate from one to another using the arrow keys on your keyboard, or to jump
around more, click the thumbnail button again, then select a photo, then click the preview
button again.
Once you've done this a few times, it becomes second nature.
So that brings me to one of the first fixes I have had to do.
And that is what I call fingers and photos.
These days I take nearly all of my photos with my Android phone, because the quality
is good enough that there is no need to do anything else.
And I want to emphasize, I am not a professional photographer, or even an advanced photo hobbyist.
I'm a guy that likes to travel and take vacation photos.
So I'm not trying to do anything super fancy.
And really these days my Android phone is pretty darn good.
And it means I don't have to lug around any equipment, because I will always have my
phone handy.
But this does have one potential downfall, and that is an errant bit of a finger in the
photo.
Now I recently, as I'm recording this, came back from a month-long visit to France and
had quite a few photos.
Well, you know, you spend a whole month someplace that's going to happen.
And some of them had this fault.
And I've gotten, in general, pretty good about being conscious of getting my fingers out
of the way.
But when you're taking pictures with a cell phone, a smartphone, whatever, it's really easy
to get just a little bit of the finger into the photo.
And you know, that's not good.
So I want to fix it.
And it really, the way I do it is a simple fix.
I just cut out the bad part.
Now this starts with DigiCam, where I load up a directory of a day's photos and click
the preview button and scroll through the photos one at a time.
When I find one that has the errant finger, I check the file name of the photo, then
open it in GIMP.
The first dialog box I deal with is about changing the color scheme, and I always tell
it to keep the original scheme and not convert it.
I'm not trying to do anything major here to just cut out the finger.
Now when the photo opens in GIMP, I select the crop tool, and I drag it to exclude the
errant finger.
In other words, the crop tool is used to select what I want to keep from the original
photo, and that should be most of it.
Generally the errant finger is at the top of the photo and covers no more than 5 or 6%
of the vertical distance.
When it's correctly selected, you hit the Enter key, and the part outside the crop will
now disappear.
Now I go to the File menu and find the option to overwrite the original file, and when
I do this, a pop-up window appears and I click Export.
The last step is to go back into DigiCam and click the Refresh option in the View menu,
or pressing F5 will do the same thing.
This will cause DigiCam to reread the file from the hard drive.
I find the file I changed in the thumbnails, click the Preview, and make sure it is the
way I want it.
If it is, I can then resume scanning the photos using the arrow key until I find another
one that I need to fix.
Well what if you don't like to change and want another shot at it?
Well at this point, if you have been following what I did, I have not yet discarded my work
and Gimp.
I can go back to Gimp and use Control Z to get back the original before my crop operation.
I don't discard my work and Gimp until I'm ready to work on a new photo.
Now of course you could also back up all of your originals into a separate archive before
you start work, but this works well enough for me.
When I get to the next photo, I start in Gimp by going to File and then Close to get rid
of the previous photo, then open the new one and continue.
So that's how I deal with the Errant Finger problem.
Now another common one is Red Eye and I think we've all seen this in a few of our photos.
It's when the pupils of the subject's eyes appear bright red, giving them a rather
satanic appearance.
The cause of this in short is light bouncing off the retina in the back of the eye, which
is rich in blood vessels, hence the bright redness.
This is generally observed in photos taken with a flash.
Once the light hits the eye and bounces back faster than the pupil can adjust.
But how do you get rid of it?
There are a number of ways, but here are some fairly simple ways to do this.
Now the first one is for low-res photos, and by low-res what I mean is when you zoom
in you see very distinct pixels, you know, they become squares.
So you load the photo and gimp, you zoom in, and you know, now you see the squares.
Then what you do is you use the color selector to make sure your selected color is black,
then select the paintbrush tool and reduce the size.
If I can see individual pixels, I set the size to 1.
This lets me operate on one pixel at a time.
Now paint out the red eye color by clicking on the individual pixels.
Now you'll probably click on each pixel several times, since it does not go to pure black
right away, and this is good because it lets you blend the pixels a little better.
Repeat for any other eyes in the photo that are red and export the finished photo when
you were done.
So that's for low-res photos, the ones that are really pixelated.
But what about high-res photos?
These days, actually most of the photos I take with my smartphone are fairly high resolution.
And what that means is when I zoom in, I am not going to see individual pixels.
It just zooms in.
So for that, I use a slightly different approach.
First load the photo and gimp, zoom in until the red spot is like three to four centimeters
across.
If this is a high-res photo, you should not see any discernible pixels.
That's the whole point, because this is a different technique for a different situation.
Then use the ellipse select tool to select the red area.
Now go just a little beyond the red area to make sure there is no red unselected.
If the eye is partially closed so that you don't have a fully round pupil, you should
use the free select tool instead.
And click around the area to make a dotted line that encloses it.
Then go to Filters, Enhance, Red Eye Removal, and click OK.
Now what you may find is that you've gotten rid of the red, but there's still some blue
or white in the pupil.
So if you want to adjust that, because that may look a little unnatural now, go to the
Colors menu, select Colorize, and turn down the Lightness and Saturation until you get
something that looks right to you.
Now finally, I want to talk about photo artifacts.
Now these can be caused in a number of ways.
There could have been a speck of dust on the lens when you were trying to take the picture.
Something may have happened to the negative.
So you know, the picture is just there's something wrong here.
Now I have a photo of my wife.
It has a little white streak on her eyelid.
Now that to me looks like damage to the negative.
It's not that hard to fix something like that.
So what you do is you first load the photo in Gimp, zoom in to the spot that needs to be
fixed.
Now go to Tools, Paint Tools, Heal.
So the Heal tool is one of the paint tools, and that's the key to this.
Now what does that do?
This tool lets you grab pixels from a different part of the picture and paint them over an area.
Now the key thing to keep in mind is that the pixels being grabbed are in relationship to
what you are painting.
So in this case, I'm looking at my wife's eyelid and there's this white streak.
Well I'll just go a little bit to the right of the white streak and get the normal eyelid
and click there.
Now what's going to happen is that you select by holding down Control Click in the area
you want to grab the pixels from.
And then with just a regular paintbrush option, because this is the Heal is a paint tool.
You can paint over the artifact, but as you do that, let's say you're moving your paint
brush up, the area being grabbed from moves up as well.
So if you started by grabbing pixels, let's say, you know, three centimeters to the right
of where you are painting, as you paint the area being grabbed also moves the same way.
So there's always three centimeters to the right of wherever you're painting.
Now that can cause you to paint something you didn't intend.
And if that happens, just release the tool and start again.
Now as you're setting this up, make sure you have your tool option dialog open so you
can control the brush size and things like that and set the brush size.
I would suggest something like 15 to 20, but you can try different sizes to see how it
works for you.
Now you go to the area you want to grab pixels from and Control Click.
Now you should see a dotted or dashed circle that is going to be, however many, you know,
correspond to the brush size you selected.
And so that's tells you what you're grabbing.
Now if that's all pretty uniform in that area, you're fine.
If there's variation, you might want to change the brush size so you're only picking up
the part that you want.
And then you just paint the area you want to heal.
And you should see the pixels change as you paint over them.
So for instance, this photo is my wife's eyelid, but the streak went into the eyebrow.
So at a certain point, I had to stop painting where I was and now I want to grab from
another part of the eyebrow to fix that.
So you see what I mean about how you have to be careful about where you're grabbing
and what you're painting over.
Now remember, if at any point you say, oh, that was a mistake, Control Z will always get
you back again.
So you know, and the other thing is you can paint over something several different times
until you get it the way you want it.
So just go through this process until you have a picture you like.
Now for a more detailed look at this, if you really want to dig into how to use the
heal tool, I'm going to put a link in the show notes to a video from Davies Media that
you might want to take a look at.
And by the way, that photo of my wife now looks much better.
I also corrected some red eye in the photo because photos often have several things to
be corrected.
Now with a little practice, you'll find you can use these tools quite easily to improve
some of the issues in your photos.
Now I'm going to do at least one more of these to address a couple of more issues that
I have been running into with my photos.
And one of them is about photos that are just too dark.
You know, is there any way I can lighten it up?
The other one has to do with old photos where the colors have gone wonky and that can
happen.
You know, I've got some photos that are 50 or 60 years old and the negatives may not
have survived as well as they should have.
So I'm going to do those.
Anyway, for now, this is Ahuka for Hacker Public Radio signing off and is always encouraging
you to support free software.
Bye bye.
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